The rings are super magnets.
If the rings are super magnets they can accelerate ships via electromagnetic repulsion. A set of rings, for example 10 or 100 can be used to apply the repulsion affect several time to accelerate a ship very fast forward. You may want to have a corresponding set of rings on the other side, at the destination, to decelerate incoming ships in the same way to make this system really efficient.
Is it practical? It is probably a lot more practical than using rocket fuel. The ships can be lighter since they don't have to carry the fuel themselves. So they can be smaller, cheaper, etc. Building rings like this in space probably isn't too difficult either since the mechanics behind it and the size are not too absurd.
Coordinating everything so that they line up would be the hardest part. This is because planets move. So lining up the rings for acceleration at your departure point, so that you reach the rings for deceleration at your arrival point, may be a difficult math equation to solve.
So how do we address the problem that when a ship moves forward it will push the rings backwards? (Newtons 3rd law)
The rings don't have to be completely stationary satellites. They can be space ships too, but designed to just stay around some region of space.
The rings can even be one large super object instead of separate rings, or attached to asteroids, and be re-attachable to others when one moves too far.
The rings can have all the usual bells and whistles for navigation. How bulky the rings are isn't really an issue for interstellar travel since they wont be travelling far. The real benefit is in having the ships that are ejected not have to carry lots of fuel, so they can be accelerated to very fast speeds fairly efficiently. This is because the ships can lower their mass by shedding the mass of their fuel, which is instead handled via the electromagnetic ring.
Force = Mass x Acceleration,
Acceleration = Force / Mass.
By lowering mass we can increase the amount of acceleration from the same force.
And Thanks @Alice:
There are also ways to maintain or correct orbit without expending
reaction mass, such as solar sails and tethers.